Photochromic conjugated polymers main chain

Here, we have designed and synthesized multifunctional poly(bithienylene-phenylene)s with either racemic (Poly-9) (M — 14,000) or chiral moieties ((/ )-/ (S)-Poly-lO (Mn = 10,000, 8,000, respectively), which exhibit fluorescence, liquid crystallinity, and photoresponsive properties (Fig. 11.20). The polymers are composed of a 7t-conjugated main chain, poly(bithienylene-phenylene), which acts as a fluorescence moiety and mesogen core, and photochromic DE moieties [71, 72] are linked with racemic or chiral alkyl groups in the side chains. The DE photoresponsive moiety isomerizes between its closed and open forms upon irradiation of UV and visible light, respectively. 

Photochromic diarylethenes can be incorporated into polymers by following free-radical polymerization [75], polycondensation [76], Fridel-Crafts alkylation [77], or oxidative polymerization [78], The side-chain and main-chain homopolymers, copolymers, block copolymers, and jr-conjugated polymers synthesized by the above-mentioned methods have shown good photochromic properties in films and solution phase owing to the higher content of diarylethene chromophores in the polymer system compared to that in simple guest-host systems [79-81], Selected examples are illustrated in Figure 9.8. 

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